In test in vitro, the effects of them on chicken peripheral lymphocyte proliferation were determined by MTT method. The results showed that EP–PF group presented the highest stimulating index at most concentrations. In immune test, 300 14-day-old chickens were randomly divided into six groups and vaccinated with ND vaccine except for blank control (BC) group, re-challenged at 28 days of age. At the same time of the first vaccination, the chickens in four experimental groups were injected, respectively, with four prescriptions. The changes of the lymphocyte proliferation and antibody titer were determined. On day 28 after the first vaccination, the chickens except for BC group were challenged with NDV, the immune protective effect was observed.

The results displayed that in EP–PF group, the antibody titers, lymphocyte proliferation and protective rate were the highest, the morbidity and mortality were the lowest. In dose test, 14-day-old chickens were randomly divided into five groups. The treatment and determinations were the same as the immune test except that the chickens in experimental groups were injected, respectively, with high, medium and low doses of EP–PF.

The results revealed that in medium dose group, the antibody titers, lymphocyte proliferation and protective rate were the highest, the morbidity and mortality were the lowest.

These results indicated that EP and PF possessed synergistically immune enhancement, EP–PF had the best efficacy, especially at medium dose, and would be expected to exploit into a new-type immunopotentiator.